This invention relates to an actuator of a variable compression ratio mechanism arranged to vary a mechanical actual compression ratio of an internal combustion engine, and a link mechanism used for a variable valve actuating apparatus that is arranged to vary operation characteristics of engine valve of an intake valve and/or an exhaust valve.
A Japanese Patent Application Publication No. 2011-169152 discloses a conventional variable compression ratio mechanism which uses multi-link piston-crank mechanism, and which is arranged to vary a mechanical compression ratio and a geometric compression ratio of the internal combustion engine.
That is, a piston and a crank shaft are connected through an upper link and a lower link. A posture of the lower link is controlled by controlling the actuator. With this, the engine compression ratio is controlled.
The actuator includes a housing, a speed reduction device and a drive motor which are mounted to an outside of the housing, and a control shaft (a second control shaft in the above-described patent document) which is inserted within the housing, which are rotatably supported, and to which a rotational force from the speed reduction device is transmitted, and an eccentric shaft portion (a second eccentric shaft portion in the above-described patent document) which is integrally provided to a tip end of the control shaft, and a control link which includes a first end connected to a lower link, and a second end connected to an eccentric shaft portion of the control shaft that extends in parallel with a crank shaft.
A rotation position of the control shaft is varied by the rotational force from the drive motor and the speed reduction device. With this, a posture of the lower link is controlled through the eccentric shaft portion and the control link.